Synthesis of glass–ceramic Li7−2xZnxP2S8–xOxI oxysulfide solid electrolyte with high chemical stability for all-solid-state lithium batteries

Abstract

All-solid-state batteries remain problems to be overcome due to the high-temperature heat-treatment process, and the compatibility problem with Li metal as an anode. In this work, Li7P2S8I (LPSI) solid electrolyte with high ionic conductivity is prepared using a high-energy dry ball milling process with a low-temperature (200 °C) heat-treatment process. Then, ZnO are doped with LPSI solid electrolyte, particularly Zn2+ at the Li site and O2− at the S site, by our optimized synthesis process. The ZnO co-doping is confirmed by powder X-ray diffraction, Laser–Raman, field emission scanning electron microscopy, and nuclear magnetic resonance spectroscopy analysis. The ionic conductivity value of the prepared solid electrolytes is measured by electrochemical impedance spectroscopy analysis, and the prepared LPSI and Li6.9Zn0.05P2S7.95O0.05I solid electrolytes exhibit an ionic conductivity of (4.4 and 4.2) mS·cm−1, respectively, at room temperature. To evaluate the electrochemical stability of the prepared solid electrolyte, we perform cyclic voltammetry and galvanostatic discharge/charge voltage profiles analysis. In addition, the fabricated all-solid-state battery exhibits a high specific capacity of 165.4 mAh·g−1 (0.1 C), and a high-capacity retention rate of 95.2 %. Interestingly, ZnO co-doped LPSI solid electrolyte exhibits longer air-stability than the undoped LPSI solid electrolyte in dry air with 10 % humidity.